Anatomy of a Bicycle Friendly Street: Loop Detectors

We’re back today with another installment of what surely is your favorite bicycle infrastructure series. Last time out we covered Traffic Diverters – the Cadillac of BFS treatments. This week we’ll look at a much smaller, but no less important, treatment in the:

Anatomy of a Bicycle Friendly Street

Loop Detectors

Placing your bicycle correctly makes for a much more enjoyable ride

(Ed Note: Most information on Bicycle Friendly Street treatments come from the Technical Design Handbook in the draft 2010 LA Bike Plan. Though we are happy to present it in bite-sized pieces, we highly recommend you download it yourself and have a good read. You can download the Technical Design Handbook here. For a refresher on what a Bicycle Friendly Street is -sometimes called a Bike Boulevard- you can read our introductory post here.)

Listed as a “Type 3” treatment for a Bicycle Friendly Street, loop detector symbols sit dead center in the range of street treatments. While we’ll go into the specifics of how loop detector symbols can be utilized in a Bicycle Friendly Street, we should first cover what loop detectors are and how they work.

Changing Lights with Loops

Loop detectors are coils of wire set into the pavement which, after they are electromagnetically triggered, alert traffic lights to change in the direction you are traveling. There’s a good amount of the hard science on the subject, which you can read more about here.

The takeaway is this: putting your bicycle over a loop detector should make the light change faster.

It's not the weight, it's the magnetic field

Interestingly, it’s not the weight of the bicycle that trips the loop detector, it’s the metal in your bicycle interacting with the electricity running through the loop detector. This does mean, unfortunately, that carbon-fiber bicycles may not have enough metal to set off loop detectors. Since 2007, California state law (with the passage of AB 1581) requires all new loop detectors to be sensitive enough to pick up bicycles. Bicycle detection at intersections is also now part of the CA MUTCD, contained in Part 4 (pages 67-68 & 88-90) and Part 9 (pages 32 & 44).

Not All Loop Detectors Are the Same

There are a whole range of loop detectors out there, and some are easier to use than others when you’re riding a bike. There can be “Circular Loops”, “Square Loops”, “Q Loops”, and “D Loops”. With all loops involved, it is key to have your bike on the outside of the loop and not in the middle. If your bike is perpendicular to the loops, the electromagnetic signal may not be disrupted enough to trigger the signal. In this case, a picture is far more illustrative than a description:

From the California Association of Bicycling Organizations

The City of Los Angeles currently uses circular loop detectors, the one in the top left of the graphic. The best place to put your bike at an intersection is directly over the right or left edge of the loop. Because circular loops are the least effective at picking up bicycles, the LADOT Traffic Signal Design Guidelines also call for a diagonal stripe to be put through all loop detectors adjacent to the “limit line” (the edge of the intersection) in order to better detect bicycles. Check out page 8 in the pdf linked above for a good example.

The City of Los Angeles also has loop detectors specifically built for bicycles. These typically are installed on bike lanes and resemble a smaller version of the “Square Loop” shown above.

Report Bad Loops

There aren’t many things more annoying than rolling your bike onto a loop detector and getting no response from the light. If you come across any broken loop detectors, please report them to LADOT and we’ll come out and fix or adjust them. The length of time between signal changes once a loop detector is activated can greatly vary by intersection, so please be extra certain the loop in question isn’t functioning before reporting it. The proper place to report a non-functioning loop detector is with your LADOT District Office. How do you know what district office jurisdiction you’re in? They roughly correspond to the Council Districts.

Gary Rides Bikes has documented poor loop detectors in Santa Monica

Bike Signal Stencils and More

So how does this all apply to Bicycle Friendly Streets? Well, the Technical Design Handbook calls for specialized stencils (page 44) to be painted over loop detectors on roadways receiving “Type 3” or higher treatments as Bicycle Friendly Streets.

The stencil shows you where to trip the loop detector

Combined with signal priority along the Bicycle Friendly Street, converting problematic 4-way stop intersections into signaled intersections, and installation of street-facing push buttons, stenciled loop detectors built for bicycles help turn a street into a Bicycle Friendly Street.

[…] tips on what to do if you’re in a collision; here’s my take on the same subject. A look at the signal loop detectors that makes a Bike Friendly Street bike friendly. CicLAvia is looking for volunteers for Host […]

Except for the odd way of using Sharrows signage it looks like most of these treatments could be used in Los Angeles. Wouldn’t it be great to commonly see whole families riding down streets together? That is a sure sign that bicycle infrastructure gives a sense of safety to all users.

The use of road signs that give direction to where the highlights are on the main arterials are extremely important to make these side streets valuable to even the experienced cyclists. Without them the neighborhood friendly streets will not get as much support from the fearless bicycle riders.

Fast, easy to get where you need to go and a feeling of safety are all vital to great a large increase in bicycling modal share.

Street-facing push buttons are not an acceptable alternative to in-street loop detectors. They invariably require the bicyclist to hug the curb to reach the button in exactly the place where staying away from the right curb is critical (intersections). Cyclists near the right curb are at serious risk for being right hooked. Cars wishing to turn right will line up to the left of the through-traveling bicyclist, setting up an unnecessary conflict point. Even worse is when cities place the bike push buttons to the right of a right turn lane. I hope that these push buttons are an illustration of what NOT to do rather than a feature on bike friendly streets.

A recent post on diversions reminds me that there is a real call for a demonstration project in Los Angeles to roll out some of the innovations mentioned here, least being loop detectors that work and stenciled guides. Great ideas too, but let’s think bigger and better. Rolling out a plan for an intersection featuring separated bike circulation with integrated signaling would be a great complement to the adopted bike plan (perhaps in December).

Getting the Bike Plan adopted will go a long way towards achieving that goal. When we can point to those treatments in the Technical Design Manual, we can become eligible for using federal and state funds for the project.

[…] This post was mentioned on Twitter by Barbara Hui, Di-Ann Eisnor, The BICYCLE AUTOFEED, Joseph Guisti, the anty and others. the anty said: How to trigger the stop light on your bicycle: http://bit.ly/cpMrZq […]

[…] The “Bundle of Bicycle Friendly
Streets” and “Bike Friendly Street in a
Box,” could also be programs that bring long-term change
by expanding LADOT’s tool box. The term
“Bike Friendly Streets” first appeared in the
2010 Draft Bike Plan as a replacement for Bike Boulevards.
However, the plan is unclear what a Bicycle Friendly Street
actually is, although the LADOT Bike Blog has written about some
treatments the streets could see such as roundabouts and loop
detectors. […]

[…] over 3 miles from Cochran Ave to Hoover St. It also has new bike-sensitive loop detectors which can pick up the wheel of a bicycle at each stoplight. If you’re unsure of where to place your bike to activate the signal, check out our previous […]

[…] signals can be activated by a number of different devices including bicycle sensitive loop detectors, microwave detectors, infrared detectors, video detectors, or push buttons. Per the Bike Plan TDH, […]

[…] If the light is red, be sure to stop behind the limit line (this will position you on-top of a loop detector, which alerts the traffic signal that a bicycle is present). When the train clears and the light […]

[…] If the light is red, be sure to stop behind the limit line (this will position you on-top of a loop detector, which alerts the traffic signal that a bicycle is present). When the train clears and the light […]

[…] better than loops sawcut parallel and perpendicular to the direction of travel. The article Anatomy of a Bicycle Friendly Street: Loop Detectors at LADOT Bike Blog has a really good explanation on how to reliably detect bicycles with loop […]